Why we use Spanning Tree Protocol in the Switches?

Without any loop removing mechanism, switches will flood broadcasts endlessly throughout the network. This is known as broadcast storm.

Duplicate Frame copies

A device could receive duplicate copies of same frame from different switches. It creates additional overhead on the network.

Unstable MAC Table

When switch receives a frame, it checks source MAC address in frame and associate that interface with finding MAC address. Next time when switch receives a frame for this MAC address, it will forward that frame from this interface. These entries are stored in MAC Address Table. Switch uses MAC Address Table to forward the frame. Looped network can make MAC Address Table unstable.